1. Field of the Embodiment
This embodiment relates to a backlight module and specifically to a backlight module having a plurality of light guide plates with microstructure layers disposed thereon.
2. Description of the Prior Art
Display panels and flat displays using the display panels are now the mainstream in display technology, wherein the liquid crystal display panels are especially popular in the flat display technology and are now used extensively in electronic products such as monitors, home flat televisions, personal computers, monitors of the laptop computers, mobile phones, and display screens of digital cameras.
A backlight module is a crucial element in the conventional liquid crystal display. Liquid crystal itself does not generate light and the backlight module is used to provide the liquid crystal display panel with adequate and evenly distributed luminance for the liquid crystal display panel to generate images. The conventional backlight module uses only one light guide plate to guide the lights generated by the light sources, wherein luminance at every portion of the light guide plate is substantially the same. However, the backlight module will need to make adjustment in the structure of the light guide plate, in order to generate different luminance at different parts of the backlight module separately.
FIG. 1 is a schematic view illustrating a conventional backlight module 10. The conventional backlight module 10 includes a light guide portion 20 and a plurality of light sources 40, wherein those light sources 40 are disposed at two sides of the light guide portion 20 and emitting lights toward the light guide portion 20. As FIG. 1 shows, the light guide portion 20 includes a plurality of light guide plates 30, wherein each of the light sources 40 is disposed at one side of one of the light guide plates 30 and emits light toward the corresponding light guide plate 30. Furthermore, the bottom of each light guide plate 30 is disposed with a microstructure layer (not illustrated) to break the total internal reflection of lights travelling within the light guide portion 20 so that those lights can emerge from one side of the light guide plate 30 opposite to the microstructure layer.
Each one of the light guide plates 30 corresponds to a different portion of the light guide portion 20 and the conventional backlight module 10 can individually drive the light sources 40 to generate light emerging from different light guide plates 30. In this way, the conventional backlight module 10 can provide the visual effect of light areas being lit up separately.
Light generated by each of the light sources 40 is received by the corresponding light guide plate 30 and this shows that different portions of the conventional backlight module 10 illustrated in FIG. 1 can provide luminance separately by driving the corresponding light sources 40. However, a portion of light will inevitably travel toward the adjacent light guide plates 30 and emerge from surfaces of the adjacent light guide plates 30 opposite to the microstructure layer, thus creating light leakages at the boundaries of light guide plates 30. The light guide portion 20 of the conventional backlight module 10 is composed of a plurality of light guide plates 30 assembled together and therefore visible differences in luminance and chroma occur at the gaps between the light guide plates 30. In this way, viewers can easily recognize the gaps between light guide plates 30 from the visible differences in luminance and chroma. Furthermore, the process of assembling light guide plates 30 into the light guide portion 20 is cumbersome and requires great precision. In this way, deviation between light guide plates 30 occurs under external forces and thus prevents the backlight module 10 from providing the desired optical effect.
The undesired visual effects described above affect the overall visual experience of viewers. Therefore the question of how to create light areas while reducing light leakages and visible differences of luminance and chroma is indeed one of the important issues in the backlight module manufacturing.